Polishing apparatus and method of polishing a subject

ABSTRACT

A polishing apparatus. The polishing apparatus has an abrasive cloth and a table to rotate the abrasive cloth. A holder holds a subject to be polished against the abrasive cloth. A discharger discharges a polishing solution from the abrasive cloth after the polishing solution passes between the abrasive cloth and the subject.

CROSS REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2004-089296 filed on Mar. 25, 2004, the entire contents of which are incorporated herein by reference.

BACKGROUND

1. TECHNICAL FIELD

This invention relates to a polishing apparatus and a method of polishing a subject, in particular, to a polishing apparatus using chemical mechanical polishing (CMP) method and a method of polishing a subject using the CMP method.

2. DESCRIPTION OF THE RELATED ART

FIGS. 10 and 11 show methods to supply a polishing solution to an abrasive cloth bonded on a rotary table. A subject to be polished is arranged on the abrasive cloth.

FIG. 10 is a schematic diagram of a polishing apparatus shown in FIG. 7 of Japanese Patent Disclosure (kokai) No. 07-156063. The polishing apparatus is provided with a pump 73 to supply a polishing solution 72 contained in a container 71 onto an abrasive cloth 76 bonded on a top surface of a rotary table 75. A wafer W on abrasive cloth 76 is polished by the supplied polishing solution 72. A funnel 77 receives polishing solution 72 driven off the surface of rotary table 75 by a centrifugal force. The received polishing solution 72 is drained as waste liquid 78 without circulating.

FIG. 11 shows another polishing apparatus shown in FIG. 1 of the same Japanese Patent Disclosure. The polishing apparatus is provided with a plate 2 directing toward a rotational center 3 of a rotary table 1, in order to let a polishing solution flow toward rotational center 3, which polishing solution would have been driven off the surface of the rotary table 1 without plate 2. In other words, plate 2 dams up the polishing solution and exerts force in a radially inward direction of rotary table 1 on the dammed polishing solution.

The method of supplying polishing solution 72 shown in FIG. 10 is expensive since almost all of the polishing solution 72 supplied onto the surface of abrasive cloth 76 is driven off without being used for the polishing. Then, the actual amount of polishing solution 72 supplied between wafer W and abrasive cloth 76 is quite limited. In other words, an application efficiency of polishing solution 72 is so low that a cost of a polishing process becomes high. The polishing apparatus shown in FIG. 11 is also not efficient since the apparatus does not have a distinguished polishing rate.

SUMMARY

There is a polishing apparatus consistent with the present invention. The apparatus comprises an abrasive cloth, a table to rotate the abrasive cloth, a holder configured to hold a subject to be polished against the abrasive cloth, and a discharger to discharge a polishing solution from the abrasive cloth after the polishing solution passes between the abrasive cloth and the subject.

In this invention, an abrasive cloth includes a polishing pad ,and a table includes a rotary table or a platen, and a holder includes top ring or polishing head or wafer carrier.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic diagram of a polishing apparatus 100.

FIG. 2 is a schematic plan view of a rotary table 1 of polishing apparatus 100.

FIG. 3 is a drawing to define an angle of a plate 6.

FIG. 4 shows a relation between a kind of a slurry and a pH value.

FIG. 5 shows a relation between a pH value and a polishing rate.

FIG. 6 shows a relation between a flow rate and a polishing rate.

FIG. 7 is a schematic diagram of a polishing apparatus 200.

FIG. 8 is a schematic diagram of a polishing apparatus 300.

FIG. 9 is a schematic diagram of a polishing apparatus 400.

FIG. 10 is a schematic diagram of a conventional polishing apparatus.

FIG. 11 is a plan view of a rotary table 1 of another conventional polishing apparatus.

DETAILED DESCRIPTION

A first embodiment consistent with the present invention is explained with reference to FIGS. 1 to 6.

The inventors of the present invention have identified that a pH value of a used slurry (a used polishing solution) is lower than that of an unused slurry, and that a polishing rate deteriorates with a lowering of a pH value of a slurry. The inventors have concluded that reducing slurry consumption only by circulating a used slurry is of limited value.

In this embodiment, a used slurry is not tried to be accumulated or maintained on a surface of an abrasive cloth but willingly discharged from the surface of the abrasive cloth.

FIG. 1 shows a schematic diagram of a polishing apparatus 100.

Polishing apparatus 100 is provided with a rotary table 9 (table) rotated by a motor (not shown), an abrasive cloth 1 bonded on the top surface of rotary table 9 and a top ring 2 (holder) to hold and rotate a subject to be polished such as a semiconductor wafer. Top ring 2 is movably arranged. Polishing apparatus 100 is also provided with a polishing solution supplying mechanism 3 to supply a polishing solution onto abrasive cloth 1, and a plate 6 (discharger) to dam up a used polishing solution and discharge it off abrasive cloth 1. A first arm 20 supports supplying mechanism 3 arranged above abrasive cloth 1. A second arm 22 whose position and angle are changeable secures plate 6 above abrasive cloth 1 on rotary table 9. A third arm 24 supports top ring 2 which rotates on its axis.

Plate 6 may made of polycarbonate or fluorocarbon resin which are alcaliproof. However, other materials can be substituted. When worn, plate 6 can be replaced.

As to plate 6, a flat plate or a curbed plate may be used. Further, a circular plate, a spiral plate or a plurality of flat plates may be used. Moreover, an absorber to absorb a used polishing solution off abrasive cloth 1 or a blower to blow high-pressured air in a radially outward direction of the rotary table to blow a used polishing solution may be used instead of plate 6. Moreover, a suction unit to suck in a used polishing solution on abrasive cloth 1 may be used. Other ways to discharge a used polishing solution from the surface of abrasive cloth 1 may be substituted for plate 6.

An operation of polishing apparatus 100 will be explained next. A polishing solution is supplied onto a dripping position (supplying position) of abrasive cloth 1 while rotary table 9 with abrasive cloth 1 rotates. Plate 6 is arranged above abrasive cloth 1 in advance. Top ring 2 holding the subject to be polished rotates. Thus, the subject is polished. FIG. 2 shows a current direction of the polishing solution (slurry) on abrasive cloth 1.

A side wall of plate 6 facing top ring 2 is defined as an A-side (FIG. 2), and the other side wall facing the dripping position is defined as a B-side in this embodiment. Used slurry, after passing between the subject and abrasive cloth 1 collides with the A-side of plate 6. Then, plate 6 exerts force on the collided slurry in a radially outward direction of abrasive cloth 1 (rotary table 9). The used slurry moves along with the A-side. Consequently, the used slurry is discharged from abrasive cloth 1. Meanwhile, unused slurry which does not flow between the subject and abrasive cloth 1 collides with the B-side. The B-side exerts force on the collided unused slurry in a radially inward direction of abrasive cloth 1 (rotary table 9) so that the collided unused slurry moves toward the subject.

Next, a position of plate 6 will be explained in detail with reference to FIG. 3. As shown in FIGS. 2 and 3, plate 6 is arranged on an upstream side of the supplying position of the polishing solution, and arranged on a downstream side of top ring 2 so that plate 6 can effectively discharge the used polishing solution.

As shown in FIG. 3, an inclination of plate 6, which has a flat wall, is defined as an angle with reference to a plane which passes through the rotational axes of both the rotary table 9 and the center of the top ring 2, assuming the clockwise rotation viewed from the top face of rotary table 9 is positive.

In this embodiment, plate 6 is aligned with the angle θ ranging from −10 through −90 degrees.

The surface of abrasive cloth 1 has two areas divided by the line passing through the center of both the top ring 2 and the rotary table 9. When the dripping position is involved in one area, the plate 6 is arranged so as to be substantially involved in the other area in a plan view. In other words, a plane which passes through the rotational axes of both rotary table 9 and top ring 2 separates a region where almost all of plate 6 is involved from the other region where the dripping position is involved.

FIG. 5 shows a relation between a kind of a slurry and a pH value. As shown in FIG. 5, the pH value of the unused slurry is the highest; a pH value of the used slurry is the lowest; and the slurry in this embodiment is median.

FIG. 4 shows pH values of an unused slurry, a repeatedly used slurry and a slurry on abrasive cloth 1 in this embodiment. As shown in FIG. 4, a polishing rate improves as a pH value becomes high. Therefore, a pH value of a slurry on abrasive cloth 1 is maintained to keep a high polishing value by discharging the used slurry from abrasive cloth 1. Consequently, the polishing rate of the slurry in this embodiment is superior to that of the used slurry.

FIG. 6 shows a relation between a flow rate of a slurry and a polishing rate. In the figure, a 100% polishing rate is equal to a polishing rate accomplished by the conventional method using a 100% flow rate.

Using the method shown in this embodiment, the flow rate can be reduced by 70% without deteriorating the polishing rate.

A second embodiment is shown with reference to FIG. 7. An absorber to absorb used polishing solution is used instead of plate 6. As to the absorber, a material having a permeability and a porosity, such as a sponge, may be used. As shown in FIG. 7, a compression roller 12 squeezes the polishing solution absorbed by a sponge roller 11 to discharge the used polishing solution from the surface of abrasive cloth 1. The squeezed out polishing solution is drained with a trough 13. While squeezing, both the sponge roller 11 and the compression roller 12 rotate.

A third embodiment is shown with reference to FIG. 8. As shown in FIG. 8, a suction nozzle (suction unit) instead of plate 6 may be used to remove used polishing solution.

A fourth embodiment is described next with reference to FIG. 9. High-pressured air instead of plate 6 may be used. An air nozzle 16 (blower) blows used slurry off abrasive cloth 1. Other means to discharge a used slurry from abrasive cloth 1 may be used.

As well as discharging a used slurry, an unused slurry can be recirculated and reused. In the first embodiment, plate 6 both discharges a used slurry and circulates an unused slurry.

In these embodiments, a polishing solution includes a fluid or a liquid containing an abrasive.

Numerous modifications of the present invention are possible in light of the above teachings. It is therefore to be understood that, within the scope of the appended claims, the present invention can be practiced in a manner other than as specifically described herein. 

1. A polishing apparatus, comprising: an abrasive cloth; a table to rotate the abrasive cloth; a holder configured to hold a subject to be polished against the abrasive cloth; and a discharger to discharge a polishing solution from the abrasive cloth after the polishing solution passes between the abrasive cloth and the subject
 2. A polishing apparatus according to claim 1, further comprising a supplying mechanism to supply the polishing solution onto the abrasive cloth.
 3. A polishing apparatus according to claim 1, wherein the discharger comprises a dam.
 4. A polishing apparatus according to claim 1, wherein the holder comprises a top ring to rotate the subject, the discharger comprises a flat wall, and an inclination of the flat wall with reference to a plane which passes through a rotational axis of both the rotary table and the top ring is −10 through −90 degrees with the clockwise rotation viewed from the top face of the rotary table assumed to be positive.
 5. A polishing apparatus according to claim 1, wherein the discharger comprises a blower.
 6. A polishing apparatus according to claim 1, wherein the discharger comprises an absorber to absorb the polishing solution.
 7. A polishing apparatus according to claim 1, wherein the discharger comprises a suction unit to suck in the polishing solution.
 8. A polishing apparatus according to claim 1, wherein the abrasive cloth is bonded on the top surface of the rotary table.
 9. A polishing apparatus according to claim 2, wherein the discharger comprises a plate to dam the polishing solution, and wherein the plate is up the polishing solution stream from the supplying mechanism.
 10. A polishing apparatus according to claim 3, wherein the dam exerts force on the polishing solution in a radially outward direction of the rotary table.
 11. A polishing apparatus according to claim 3, wherein the dam includes a flat wall to dam the polishing solution.
 12. A polishing apparatus according to claim 3, wherein the dam includes a curved wall to dam the polishing solution.
 13. A polishing apparatus according to claim 9, wherein the holder is a top ring to rotate the subject and wherein a plane which passes through a rotational axes of both the rotary table and the top ring separates the plate from the supplying mechanism.
 14. A method of polishing a subject, comprising: rotating an abrasive cloth; providing a polishing solution between the subject and the abrasive cloth; and discharging the polishing solution from the abrasive cloth after the polishing solution passes between the subject and the abrasive cloth.
 15. A method of polishing a subject according to claim 14, wherein rotating an abrasive cloth includes rotating an abrasive cloth on a rotary table.
 16. A method of polishing a subject according to claim 15, wherein discharging the polishing solution includes exerting force on the polishing solution in a radially outward direction of the rotary table.
 17. A method of polishing a subject according to claim 16, wherein exerting force on the polishing solution includes exerting force on the polishing solution using a plate.
 18. A method of polishing a subject according to claim 16, wherein exerting force on the polishing solution includes blowing air toward the polishing solution in a radially outward direction of the rotary table.
 19. A method of polishing a subject according to claim 14, wherein discharging the polishing solution includes absorbing the polishing solution.
 20. A method of polishing a subject according to claim 14, wherein discharging the polishing solution includes sucking in the polishing solution. 